The present invention relates to a vented tire mold that includes a surface that forms the tread surface of a tire and is provided on a segment member that has integrally formed thereon projecting ribs to form a corresponding profiling in the tread surface of the tire, with the ribs having side surfaces that extend essentially perpendicular or at an angle to the surface of the segment member. The present invention also relates to a tire having a profiled tread surface.
Tire molds of this type are provided with ribs that are formed on a segment member. These ribs produce a corresponding profiled recess or groove on the tire that is produced with the tire mold. Such a tire mold must permit a venting during the tire-molding process, so that the air that is trapped in the profiling can be withdrawn during the molding process and a uniform tire surface can be produced.
To vent tire molds, it is known to provide an inclined recess on the sides of the ribs of the segment member; air that remains, and always also a portion of the rubber mixture, can enter this inclined recess. When the mold is removed, the resulting rubber plugs are to be unilaterally torn off. Although with this approach separate venting channels can be avoided, the drawback results that the remaining rubber plugs must be removed from the tire via a special trimming machine. A further drawback is that the tire mold must be cleaned after each molding process in order to remove any residue that might remain.
To avoid these drawbacks, it is known to provide the tire mold with venting holes that are interconnected via a venting channel that is connected to a vacuum source. With this type of tire mold, however, a reliable withdrawal of the air is possible only with very simple profilings that have no transverse ribs, or with such profilings where possible trapped air at the transverse ribs can be taken into consideration.
Finally, with tire molds, especially for tires of trucks and large commercial agricultural vehicles, it is known to bolt or otherwise secure the ribs on a tread mold as a separate component and to provide respective venting slits at the bases of the ribs. However, tire molds having riveted or screwed-on ribs are relatively expensive.
It is furthermore known to make each of the individual segment members relatively small, so that the tire mold then comprises a plurality of segments. The venting is then respectively effected at the abutment faces of the segment members, which do not adjoin one another in a completely sealing manner. Unfortunately, this type of venting is inclined to clogging, so that after a relatively short period of use, the entire tire mold must be taken apart and the individual segment bodies must each be cleaned.
It is furthermore known to insert into the tire mold, which can, for example, be made of aluminum, lamellae of a material other than aluminum, such as sheet steel, and to utilize the manufacturing-related slits between the lamellae insert and the mold for the venting. Such lamellae are either provided as profiling lamellae or as true venting lamellae inserts, that are provided, for example, at the base of the ribs, whereby the lamellae inserts should then end flush with the tread surface. In order to provide cross-sectional slit areas that are adequate for the venting, either a number of venting lamellae must be provided, which means a considerable additional expense, or an attempt must be made to produce an adequate slit width.
However, because of the slits that extend over their entire length, the lamellae inserts tend to loosen, so that it has also become known to produce a positive connection during casting of the mold via openings formed in the lamellae.
One aspect that negates use of the known lamellae insert ventings is the fact that although the width of the slits can be kept small, so that generally no or very little rubber can enter the venting slits, if this is the case small kernels that still result at these locations tend during repeated use of the mold to increase in size and hence to eventually cause a blockage; the removal of the residual rubber that is found there is then very difficult due to the good adhesion in the slit.
This positive connection obstructs the venting somewhat and above all forms a blockage that for all practical purposes cannot be cleaned if rubber mixture gets into the slit. For this reason, the conversion has again been made to provide venting holes at the critical locations, i.e. those locations where the longitudinal and transverse ribs come together at an acute angle, in which connection the formation of rubber plugs is taken into account, whereby these rubber plugs then have to be removed with an appropriate trimming machine.
It is therefore an object of the present invention to provide a vented tire mold and tire of the aforementioned general types that, with respect to the venting, enable a long, problem-free operation and a relatively easy cleaning without the necessity for having to dress the tire surface, and without the visual impression that the finished tire makes having to suffer.